It is written in C.  The only real reason C was used was performance
concerns, real or imagined.  I can post a diff of the changes - it isn't
that many lines.

On Dec 4, 2016 12:04 PM, "Stefan Monnier" <monnier@iro.umontreal.ca> wrote:

> > That's too bad (I mean, its good for performance, but unfortunate one of
> > the use cases doesn't exist).  However, the treap functions may still be
> of
> > general use.  Let me know if there is any interest.  They are documented
> > and tested.  They fill a gap between alists (persistent, linear lookup)
> and
> > hash tables (ephemeral, constant lookup) by being persistent while
> > providing average case logarithmic lookup.
>
> Is it written in C or Elisp?  If it's Elisp, then we definitely would
> welcome it into GNU ELPA (there is already an avl-tree implementation in
> Emacs itself at lisp/emacs-lisp/avl-tree.el, but the more the merrier).
> If it's written C, I'll let others decide whether we want to include it.
>
>
>         Stefan
>